Just like to start by saying thank you to all who have taken their time to give some thoughtful responses, and encouraged some re-planning.
This is one of those projects that uses stuff hanging about in the store cupboard or recycled. I should have noted this is 00, and geared for 'playability' for my grandson, and not prototypical really.
The operation 'must-haves' include to be able to run one train continuously, whilst the station area can be operated separately. There is a small Atlas turntable that needs to be incorporated, which I am going to try and semi-bury in the celotex of one of end boards and cobble an old Airfix kit on top.
The board is 2340 x 1220, 2 x celotex plus Ikea Bonde shelves at 385 and 190 widths.
Having set out most of the track on the boards, I agree my original plan is a very tight fit, and probably too ambitious. With that in mind, and within my very limited Anyrail knowledge - two hours and the limitations of the trial version - I present a modified design, basically removing one of the circuits.
I have based the curves on Setrack R2 and R3, and using some Streamline where transition curves are needed. The turnouts are all Streamline. Straight joints at each baseboard join to make the layout moveable in the future. The edges will have a ply backscene all round as the layout will be viewed from the operating well.
I might add a fiddle yard off the outer circuit on an extension at bottom left. On the opposite side the board is lower than datum to allow for a bridge and embankment.
Anyways, I am off to think about the electrics and see if I can mark up the Anyrail file. And identify the live frogs from the dead ones!